1. Field of the Invention
This invention relates to an improved zeolite-containing catalyst used for cracking hydrocarbon feedstocks in the absence of external hydrogen pressure.
2. Description of the Previously Published Art
For many years, cracking catalysts employing some form of faujasite type Y zeolite have been used to produce gasoline in the fluid catalytic cracking (FCC) process. Catalysts employing said zeolite in a matrix are disclosed in U.S. Pat. Nos. 3,140,249, 3,352,796, 3,647,718, 4,581,341 and 4,493,902. Recently, several disclosures have appeared which use mixtures of zeolite Y with other components to improve the octane of the resulting gasoline-range product. U.S. Pat. Nos. 3,758,403, 3,894,931, 3,894,933, 4,289,606, 4,309,279, 4,309,280 and 4,368,114 disclose the use of zeolite Y admixed with zeolite ZSM-5 in the FCC catalyst particle or the use of a mixture of two FCC catalysts, one a conventional cracking catalyst using Y and the other using ZSM-5, or the use of a conventional FCC catalyst with finely powdered ZSM-5 added to the charge stock to make higher octane gasoline. U.S. Pat. No. 4,137,152 discloses the use of catalysts composed of a mixture of Y and Mordenite. U.S. Pat. No. 4,740,292 discloses the use of catalysts composed of a mixture of zeolite Beta with a conventional zeolite Y cracking catalyst and European Patent No. 350,331 discloses the use of mixtures of zeolite L with zeolite Y catalysts, both for improved gasoline octane.
U.S. Pat. Nos. 4,340,465 and 4,614,578 disclose the use of FCC catalysts employing a ZSM-5 type zeolite with a high silica-to-alumina molar ratio (SiO.sub.2 /Al.sub.2 O.sub.3 &gt;approximately 500; also called "silicalite" in U.S. Pat. No. 4,061,724) in conjunction with a zeolite Y type cracking component to improve the octane of gasoline produced by the FCC process while reducing the gasoline yield penalty typically associated with the use of ZSM-5 type additives.
U.S. Pat. No. 4,899,007 discloses the alkylation of aromatics over metal impregnated zeolitic catalysts. The zeolite is ZSM-5 and the impregnated metals include Mg, Fe, Sr, Ca, Ba, Na, and Co.
3. Objects of the Invention
It is an object of this invention to produce a zeolite containing catalyst which improves the octane of the gasoline produced in an FCC process.
It is a further object of this invention to provide an additive to be used in conjunction with a typical FCC catalyst to improve the octane number of the gasoline product.
It is a further object of this invention to provide a partially cation-exchanged medium-pore crystalline aluminosilicate component additive to be used in conjunction with a typical FCC catalyst to improve the octane number of the gasoline while reducing the gasoline yield loss typically associated with such additives.
It is a further object of this invention to produce a modified ZSM-5 based additive to be used in conjunction with a typical FCC catalyst to improve the octane number of the gasoline while reducing the gasoline yield loss typically associated with such additives.
These and further objects will become apparent as the description of the invention proceeds.